The present invention relates generally to agricultural equipment and, more particularly, to an apparatus for controlling the helically tying by means of twine of agricultural roll bales formed in a roll baler device. In apparatus of the type to which the present invention relates, a guide member is provided for guiding twine along an intake aperture extending across the width of a bale chamber housing of the roll baler and spring means operate to pull the guide member into a lateral rest position, with the spring means being tensioned by movement of the guide member into its opposite start position with a control device automatically controlling the rate of feed of the guide member during tying operation.
In apparatus of the type to which the present invention relates known, for example, from German Pat. No. 30 07 646, the rate of feed is controlled by a cam gear. When a cam disc of the device is correctly designed for a desired tying sequence, there may result kinematically unfavorable transmission angles which lead to substantial wear particularly due to unavoidable dust in the atmosphere. The substantial speed step-down which is necessary will require complicated construction and numerous bearings and joints which will require maintenance. Additionally, the cam disc must positively transmit feed motion to the guide member against the force of a spring and against countertorque exerted by tension in the twine, and when this occurs very high transmission forces are required. In this connection, reference is made to German Offenlegungsschrift No. 26 40 563 and U.S. Pat. No. 2,468,641.
Additionally, an operator may no longer be able to influence the tying procedure during its sequence in these cases. For example, it may be desirable or necessary after commencement of the helical tying operation to apply new initial windings and to commence tying once again.
The invention is directed toward the task of providing a tying apparatus which is essentially automatically controlled and which is structurally uncomplicated, small in its dimensions, low in wear and maintenance, and relatively inexpensive. The invention is further intended to provide a mechanism wherein commencement of operation will occur with substantial safety and wherein spacings of windings which are developed will be very uniform, even when the properties of the materials may differ.